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Bulk Densification

December 31, 1997

We think of our screw presses as machines that separate flows of wet solids into a stream of dirty press liquor and damp press cake. We rarely get out a flow of clear press liquor, and there is always some moisture left in the press cake.

An unusual application was tested at the recent Sales Rep meeting. A sample of dry, fluffy paper fiber was brought to see if the air could be removed. The idea was to deaerate the material, increasing the bulk density.

Bulk densification is called for when there is a need to transport or store dry materials that are light and fluffy. In their natural state such materials are difficult to manage because they rapidly fill the storage facility or truck.

The initial trials were encouraging enough that Merfin, the paper company in British Columbia, sent larger samples to Tampa. Pressing the air dry bleached pulp fibers with a KP-6 press, it was found that the press cake occupied only one quarter of the original volume. The final cake measured 22 #/cf bulk density. During pressing there was a flow of air to be seen coming out of the press liquor discharge. A brief, interesting video was made.

Another similar application that was tested previously was to deaerate Kaolin clay that is used as a paint ingredient. These tests were successful, although there was an indication that more than normal press horsepower was required.